126 THE SPIRIT OF THE SOIL 



It is also generally true that bases are formed by 

 metals combined with the group OH e.g., NaOH, 

 etc. and that acids are formed when non-metals 

 are combined with the group OH e.g., H 2 SO 4 

 (Sulphuric Acid). 



H ~x 



H (X ^O 



But there are many exceptions, some more ap- 

 parent than real, such as HC1 (Hydrochloric Acid) 

 and all the organic acids, such as CH 3 COOH (Acetic 

 Acid), where the CH 3 group may be regarded as 

 acting as if it were a non-metal element. 



There are not many groups that we have to 

 consider for the present purpose of this book. The 

 group of chief importance is the COOH group. 

 This is the standard grouping that gives acid proper- 

 ties to organic bodies, and that can be neutralized 

 when the hydrogen in it is replaced by such a sub- 

 stance as the Calcium of Lime. The atoms are 



combined as follows : C\ QTJ> an d it will be noticed 



that the Carbon has one affinity unsatisfied. If a 

 Methyl group (CH 3 ) is linked on to this we have 

 Acetic Acid, one of the simplest of all organic bodies : 



H 



I j& 



H C C 



From this a whole series of organic acids can be 

 formed by the simple system of inserting any desired 

 number of the group CH 2 . 



